As a device to moisturize dry inhalation air supplied from an apparatus such as an anesthesia apparatus or a ventilator when using the apparatus, a heat and moisture exchanger is previously known in which a heat and moisture exchange material to capture water vapor contained in a patient's exhalation air and moisturizing inhalation air by the water vapor is provided. Such a passive device which is small, lightweight and inexpensive compared to active devices having a humidifier or heat source is less prone to problems that may potentially lead to a medical accident such as moisture shortage caused by a mistake in operating the humidifier or heat source, and is accordingly widely used in medical fields.
With regard to the heat and moisture exchanger, from the viewpoint of reducing the burden on the patient it is required to add sufficient moisture to inhalation air to maintain humidity in the inhalation air, and to keep pressure loss to be small and uniform. Further, because it does not have a mechanism to supply moisture from outside, it is important to have a moisture retention capability to capture moisture contained in inhalation air. For example, in JP-A-2006-136461, disclosed is a moisture exchanger for respiratory gas in which a supplemental heat and moisture accumulator made of corrugated paper is positioned in an opening portion on the patient side, the supplemental heat and moisture accumulator containing a hygroscopic substance such as glycols and calcium chloride.
However, in the moisture exchanger for respiratory gas described in JP '461, there is a fear that pressure loss may increase compared to conventional ones because the supplemental heat and moisture accumulator is positioned therein and, although the moisture retention capability is improved, the ventilation property is not adequately secured. Further, because the moisture exchanger requires additional processes such as a process of accommodating the supplemental heat and moisture accumulator in a housing and a process to make a hygroscopic substance be contained in the supplemental heat and moisture accumulator, it is difficult to suppress an increase in manufacturing cost.
Accordingly, it would be helpful to provide a heat and moisture exchanger of reducing a burden on a patient at low cost by a relatively simple structure that can reduce pressure loss and improve moisture retention capability.